Q.Explain any three principles of green chemistry.

Step 1. Select any three of the twelve principles (Section 16.3.1-16.3.12). As a representative example set: Prevention of Waste, Atom Economy, and Use Safer Solvents and Auxiliaries.

Step 2. Explain Prevention of Waste (16.3.1). Priority is given to preventing waste rather than treating it after it forms, illustrated by zero waste technology (ZWT), where one system's waste (e.g. thermal-power-station bottom ash) becomes another system's raw material (e.g. cement/brick manufacture).

Step 3. Explain Atom Economy (16.3.2). Atom economy measures how much of the reactants' mass ends up in the desired product; % atom economy = (formula weight of desired product / sum of formula weights of all reactants) x 100, illustrated by the butan-1-ol to 1-bromobutane conversion (49.81% atom economy).

Step 4. Explain Use Safer Solvents and Auxiliaries (16.3.5). Choose the safest available solvent for each reaction step and minimise total solvent/auxiliary use, illustrated by replacing volatile halogenated solvents (CH2Cl2, CHCl3, CCl4) with green solvents like water or supercritical CO2.

An open-choice question; any three of the twelve principles listed in Section 16.3.1-16.3.12 are acceptable, each explained with its own illustration from the text.

• Naming three principles but only stating their titles, without giving the illustrating example the text provides for each.
• Confusing two closely related principles (e.g. 'less hazardous synthesis' vs 'designing safer chemicals') and explaining only one while claiming to have covered both.